A stratovolcano, also called a composite volcano, is a tall, conical volcano composed of several layers of hardened lava, tephra, and volcanic ash. These kinds of volcanoes are characterized by a powerful and periodic, explosive eruptions. The lava that flows from them is viscous, and cools and hardens before spreading very far. The source magma of this rock is classified as acidic, having high to intermediate levels of silica (as in rhyolite, dacite, or andesite). This is in contrast to less viscous basic magma that forms shield volcanoes (such as Mauna Loa in Hawaii), which have a wide base and more gently sloping profile.

Although stratovolcanoes are sometimes called composite volcanoes, volcanologists prefer to use the term stratovolcano to distinguish among volcanoes because all volcanoes of any size have a composite (layered) structure — they are built up from sequential outpourings of eruptive materials. Stratovolcanoes are the most common types of volcanoes.